Relay control circuits for signalseeking receivers



2 Sheets-Sheet 1 D. W. COLE RELAY CONTROL CIRCUITS FOR SIGNAL-SEEKINGRECEIVERS RT w Filed June 7, 1946 March 14, 1950 INVENTOR 2.2270 W CbZeATTORNEY D. W. COLE Mgrch 14, 1950 v RELAY CONTROL CIRCUITS FORSIGNAL-SEEKING RECEIVERS 2 Sheets-Sheet 2 Filed June '7, 1946 INVENTOR.DQTYQ 5% C02? ATTORNEY Patented Mar. 14, 1950 TED RAT ounce "Rem:ooN'rRoi;cmoms-FoasmNAL- SEEKING RECEIVERS lsiDana-wefiole; Bulialo, N;.,assignor2to Colonial Radio uCorporation,lBuifalo,iN. Y.

sukplilication ilun 7, 1946,;"SeriaI'No: 6741966 Thi'siinvention reiateszto relay control? circuits r g nal seeking receivers. 1E0!QEI'IE EPUIDOSES CIE"this description, ,ia signalseeking receiver is one in whichtheltuning appafi-raitus isdri-ven by asource "of power such' as a motorand *seans the tuningspectrum =ur'1ti1- "an incoming :signal ofpredetermined strength -is 'itune'd in. I The reception of this"signal:actuates a .icontrol circuitwhich de-energizestheituner driue, rand thetreceiver w'ill th-us remain tuned to I? the incoming signal until -the"operator :puts it into .sioperatiom' to: selectsanotheri station,ratiwhichitime git willatresume :scanning zthe spectrum Sand :wm

"-agaims-topi'itselfmhenanotherrincomingasignal ofcpredeterminedzstrengtlrzis tuned-in.

iione'coftthe .difli'cfiltiesi heretofore encountered in suchreceiverszis that, because" it :takesra finite :interval: of 'atime to:operate ithe :control acircuits zaiterwtheuincomi-nga-signaljis' tunedin;ithe.;receiv.er lmayglpassithe; positionsfor ibestutnning .ibeforestile tuningaapparatus actually comes toxrestaandithis "hassnequired theusevof variouszcornectingarmangements.

(Another tdifficultyw-is -..tha,t,.because:.10f other timeiintenvalrequired for thetcontrol circuitsi-tooper- 1 .ate, the :;tuninginstrumentality .cannotsscantoo :fast. ivIf :it is attempted :to operateithe ituning instrumentality too Efast, l the :receiver may ituneJthroughannincoming signal vand-athe zsignaltma'y rbeccompl'ete'ly.tuned .Jout .bfore ithearelays have timeutoloper'ate.

.It is an obj ect of this invention to provide confltrohcircuitsiorisignal-seeking.receivers in which the length oftimeirequ-ired;forothenrelays torloperate is verysflbstaritiallydecreased.

It is v a'ffu'r ther object of this invention to provlideiisuchcontrolicircuits which operatelin responselto an incoming signal pulseof -considerlaibly shorter time duration than \wasihereto'fore possible.

I "It is atu'rther :object of this;invention'ltojprotide "control"circuits which i are JtsufficientIy *qui'k "acting to permit titheiscannirrg "speedto? vbe iconsiderabl increased.

"Still other'bbjectsand advantagesof'myinvenixtion #wi-ll fbeapparent'ifrom' thesp'eciflcation.

The features. or ':novelty which Ir beIiGVe tOELbe characteristicof'my"*i-nvention" are'set forthwith particularity'irrthe-appendedclaims.invenftiOn itsli; however "'both" as -"to itsfundamental principles andas? to "itswpaiticular-e embodiments, "will:bestbemnderstoodbyfreferen'cetothespeck fication andiaccompanyingidrawingjimwhich -Fig. Us a circuit diagram of a "signal se'eking "receiverinaceordance with my imez'ition, and

QiClaims. (015250-40) Fig. 2 is a circuitdiagram-"Ora modifiedi'form ofcontrol circuit which may be used with rthe apparatus of Fig.1.inplaceio'f'ithe' control appa- 'ratus shown' in Fig.1.

f'In the drawing, likereference numera'lszdesignate likeparts'inboth'figures.

Referring now more lparticularlyto F-ig. 1, .1 I 0 designates theantenna wiiich may 'be coupled to :a radio frequency amplifier,osctilatoraand ffirst detector, r aliindicated diagrammaticallynbyr-numeral l l The "receiver herein Sh'G-W'II i is ef 5 thesuperheterodynatypegtand the output/of therfirst detector m'ay besupplied' to the intermediate frequency amplifier 1 diagrammaticallyindicated as 1.132

A portion 'df -the output of intermediate "frequency amplifier IZ'm-ay'be passed through tuned -c0u1ol-ing circuit I 3 "and throughacrystalslecting circuit including variable-condenser l 5andpiezoelectric crystal l ly-and through condenser I B to the "controlcircuit. Preferably the-selectivity of the crystal' circuit is madequite sharpandmay -be of the-order'of 500 to 1000'-cycies"in bandwidth,an'dthis circuit willibe 'tunedto the center fre- "quency'of the I;-F.-:band.

'iithe portion of the intermediate "frequency amplifieroutput-impressedon the-control circuit isiusedx'on'ly for stopping thefreceiverftuningmt the desired point, and the rest of lithe -outputitifintermediate. frequency amplifier! 2 may beisupviilied to ,a seconddetector "and audio amplifier and: to ai'l'oud speaker in the'usualmanner.

The control circuit inlthe. embodiment shown inFig. 1 comprisesresistances l1; l8, and 1'9 connected ini'series ,With'each other, withthe output jterminal of condenser 1'6 1. connected to the common pointof resistors .iiLand I I'BVJandT towthe .control electrode ,mguof tube"20, which maybe ahard tubewhaving.cathode/200,.heaten20h, con-;trolmelectrode v20g,andanode. 20a. Cathoicleflflc may nbe ..connectedthrough resistance .523, Jaypassed by .condenser 24, to thesoppositemend of resistance J9 rfrom that tcormected itoccontrol:electrodezZlig.

Aseconditubeil maysbe provided;Jikewisohaving cathode 2 la, heater 2 lh,control electrodeaflg, andsano'cle 2 Ira. The: anode :i'may:bevconnected toztheccommonepointsofresistors .l 1 and: 1:8,sthe

i'control eiectrode toi thescommon pointsofi resistors 1 "2 5" andari 6,1thezoppositeeend-;.of :re'sistcr: 2 5;. being gether and throughresistance 22 to the common point of resistor I! and the actuating coil210 of relay 21. The other end of relay winding 210 may be connected toanode 20a of tube 20 and to the upper end of resistor 26. Relay 21 mayhave armature 2'|a and fixed contact 211), and when winding 210 isenergized, armature 21a is closed against fixed contact 2112.

Preferably armature 21a, is grounded. A second relay 30 is alsoprovided, this being a multiple type relay having actuating winding 30c,armatures 3Ual, 30a2, 30a3, and 30a4, mechanically tied together, andfixed contacts 30bl, 30b2, 30b3, and WM.

The positive side of the source of B voltage may be connected toarmature 30a4, the negative side of the B source being grounded, andwhen relay 3|] is in energized position, B voltage will be appliedthrough fixed contact 30M to anodes 20a and 2 la, through resistor l1and through actuating winding 210 of relay 21.

Armature 3|la3 and fixed contact 30b3 may be connected to mute the audiosystem by connecting the high potential side to ground when relay 30 isenergized. Armature 30112 and fixed contact 30172 serve to energizetuner motor 3| and the clutch magnet which will ordinarily be provided,to make a driving connection between tuner motor 3| and the tuninginstrumentality I la (shown as a gang condenser, although other tunersmay be used), when the receiver is to be tuned.

As stated, when relay 30 is closed, these circuits are energized fromthe source indicated as +A, the negative side of which is customarilygrounded, through motor and clutch magnet 3 |-32 in parallel and throughfiXed contact 30b2 and armature 30a2 to ground.

The remaining contacts 30b| and 30a| serve to lock in relay 30 undercontrol of relay 21, by providing for current flow from the source A+through winding 30c, contact 30b|, and armature 30a| to relay contact211) and armature 21a to ground when both relays 21 and 30 are closed.

Opening of relay 21, as will be seen, causes the energizing circuit ofrelay 30 to open and all the armatures move to open position,interrupting the +3 supply to tubes 20 and 2|, opening the audio mutingcircuit, opening the tuner motor and clutch magnet circuit, and openingthe energizing circuit for relay 30.

The apparatus will remain in this condition until switch 33 is closed.This, as will be seen, closes an alternative circuit through relaywinding 30c, actuates relay 30, and closes the circuits controlledthereby, setting the tuner to scanning the spectrum, applying platevoltage to tubes 20 and 2|, and this condition will continue as long asswitch 33 is held closed.

Supposing that the listener has the receiver turned on and wishes toselect a station, he will close switch 33 for a moment, the tuning motorwill be set in operation, and the receiver will start to scan thespectrum. When he removes his finger from switch 33, which may be aspring-restored push button, the apparatus-will not stop scanning "butwill continue until a signal is tuned in.

"' The reason for this is that if the ratio of resistance l9 to that ofresistance 25' is properly chosen, tube 20 will always be conducting,with tube 2| at cutoff, whenever plate voltage is applied, and providedthat no radio frequency voltage is simultaneousl applied to control electrode 209. Thus, relay 21 will be energized, and as long as this isenergized, relay 30 will be en- 4. ergized, the motor circuit will beclosed, and the tuner will scan.

When, however, it tunes in an incoming signal of predetermined strength,a radio frequency voltage is applied to the control electrode of tube20, and this voltage is rectified and makes the control electrode becomemore negative with respect to its cathode, thereby reducing its platecurrent. The potential of the control electrode 2| g of tube 2| willsimultaneously move in a positive direction with respect to its cathodeon account of the decreasing voltage drop across the relay winding 21,thus increasing plate current of tube 2 This further increases thenegative bias on control electrode 209 of tube 20, still furtherreducing the plate current and the ellect is cumulative and builds uprapidly to the point where tube 2| draws its maximum plate current andtube 20 goes to cutofi, thereby de-energizing relay 21, which opens, inturn de-energizing relay allowing its several contacts to open, andstopping the tuner motor and declutching it from the tuninginstrumentality.

The circuits will remain in this condition until switch 33 ismanuallyclosed to start the tuner scanning. The advantage of this arrangement isthat it permits very rapid Scanning of the tuning spectrum, since aradio frequency pulse applied to the controlelectrode of tube 20 willcause this action, even though the pulse itself is much less in timeduration than the time required for the relays to operate; that is tosay, a very much shorter pulse of radio frequency energy on controlelectrode 20g triggers the circuit off, and the action goes ahead tocompletion, although the pulse by that time may have stopped.

A somewhat modified form of control circuit is shown in Fig. 2, inwhich, since the apparatus ahead of condenser I6 is the same as that ofFig. 1, it is omitted for simplicity. The output side of condenser l6may now be connectedto the common point of resistors and 4|, the lowerend of resistor 4| being grounded and also connected through resistor 43shunted by by-pass condenser to cathode 450 of tube 45, which 'maycomprise cathode 45c, heater 45h, control electrode 459, and anode 45a.

Anode 45a may be connected through resistor 42 to the upper end ofresistor All, thence through relay contact 30M and armature 30114 to +B,as before.

Tube 46 may have cathode 460, control electrode 46g, and anode 46a.Cathode 46c may be connected through resistor 41 to cathode 450, controlelectrode 46g is connected to anode 45a, and anode 46a is connectedthrough winding 210 of relay 2! to the common point of resistors 40 and42 and through resistor 49 to cathode 460.

With this circuit, if the ratio of resistance 40 to that of resistance4| is properly chosen, tube .45 will draw full plate current on theapplication of plate voltage, again provided that a high radio frequencyvoltage is not applied to c0ntrol electrode 45g. By similar choice ofthe values of the voltage-divider resistors 49, 47 and .43,.which areconnected across the +B supply,

,tuner motor circuit will, therefore, be closed and the motor-clutchedto-the tuning instrumentality,

and the tuner will scan.

, If, now, an incoming signal is received, a radio frequency voltageiis: applied -.to :control rielectrode 45g, rectification causing :thepotential not S6011- trol' electrode 459 tozmove in .a negative=.directionwith respect to its cathode, thereby reducing the-platecurrentof tube-d5. Thei'control electrode voltage on tube a ts "willthen .become 1 more positive with respect to its cathode because :of thedecrease in voltage drcplthrough .resistorr lz.

This increases the plate current :flowing through-tubeni-e, the. cathodebias .on tuheolii .will increase in a directiontolmake control electrode45g more negative with respect to the cathode, causing still furtherreduction in plate current of tube A5. The efl'eotzisacumulative andbuilds up very rapidly to the point where tube 46 quickly passessufficientxcurrent to .energizeirelay 21, and this conditionwillcontinue asilongxas plate voltage is applied.

When relay z'l is energized, the armature moves to its contactild,opening theholdingicircuit for relay iii], permitting-this relay :toopen, I

The circuits herein describedhavea distinct advantage in that once thecircuits ;have been triggered by a carrier pulse, the relaytube willcontinue to draw current even though the .carrier pulse has dropped tozero.

In signal-seeking systems of the prior art known to applicant, the platecurrent of the relay tube is a direct time function'of the carrier-pulseand the pulse must, therefore, be of sufficient duration to permitthere-lay to iposi tively close or open. This limits the scanning speedto a value such that theirelays have time .to operate, whereas with thecircuitszhereimdescribed, the carrier pulse durationmeed: only 'be longenough to trigger the circuitgand this time is only a small fraction ofthe time requiredior vtheirelay to operate.

Thus, using circuits according.tomyiinvention, the scanning speed may beconsiderably increased without danger of the scanningb'ei'ngistoo fastfor the control system to respond and stop the scanning.

The circuits of tubes is and 2i,;in;Fig..1,"and

45 and 555, in Fig. 2, are of the classicalle'dfflipflop, and it shouldbe understood-that other circuits of this class may be employed in placeof those shown.

In the specification I have explained the principles of my invention andthe best mode in which I. have contemplated applyingthosaprinciples, soas to distinguish my .inventionirom tuning instrumeritality, said systemin' olu'ding "a 'flip-"llop circuit having an input -'circuit 'to whichis applied 'a control potential "of amplitude varying with the intensityoi' translated signal and having a 1 control circuit effective topontrolthe energization-of said-power operated F means.

'2. In a 'signal-seeking receiver, in combination, tuninginstrumentality whichis variable to a djust the tuningofsaidreceivertodesired Wave signals, power -operateol means -'energizable todrive said 'tuning instrumentality to tune said receiverover apredetermined range-of wavesignal frequencies, and a control systemrespons'ive to a predeterminedamplitude-eta received signal "translatedthrough at least a portion-of said "receiver for deenergizing said poweroperated means to terminate variation thereby "of said tuninginstrumentality, said "system including a control'arrangement having' afirst and a second operating condition and including means for providingrapid-transition fromeither 'or said operating conditions to the otherthereof, means responsive to said translated signal for causing said"control arrangement to change from one to the otherof-said-operatingconditions thereof, and means responsive to said otheroperating condition for effecting *d'eenergiZ-ation or saidpower-operated means.

3. In' a signal-seeking receiver; in combination,

"atuning instrumentality which is variable to adjust the tuning ofsaidreceiver 'to'desired wave signals, "power-"operated meansenergizable to drive said'tuning 'in'strumentality to tune saidreceiverover a predetermined range "of wave-signal frequencies, andacontrol'system responsive to a predetermined amplitude of a receivedsignal translated through at least 'a'portion of said receiver fordeenergizing said power-operated means'to terminate variation thereby ofsaid tuning instrumentalitmsaid systemin'cluding a pair ofthermionic-tube electrode structures having the electrodes thereofinterconnected to provide a flip-flop circuit with an input circuit towhich is applied a'control'potential of amplitude varying'with theintensity of said translated signal and a control circuit effective tocontrol the energization of said poWer-operated'means.

'4. In 'a signal=seeking receivenin combination, a tuninginstrumentality which is variable to adjust the'tuning of saidreceivertodesired wave signals, power operate'd means energizable to drive'saidtuning instrumentality to tune said receiver over a predetermined rangeof "wave signal frequencies, and a control system-responsive toa:predetermined amplitudeofa received signaltranslated through atleast'a portion "of-said receiver for deenergizing said power-operatedmeans 'to terminate variation thereby of said tuning "instrumentality,-said system including a pair of thermionic-tube electrodestructures'having the electrodes thereof interconnected to pro- 76 videa control arrangement having a first and a second operating conditionwith rapid transition from either of said operating conditions to theother thereof, means responsive to said translated signal for causingsaid control arrangement to change from one to the other of saidoperating Conditions thereof, and means responsive to said otheroperating condition for effecting deenergization of said power-operatedmeans.

5. In a signal-seeking receiver, in combination, a tuninginstrumentality which is variable to adjust the tuning of said receiverto desired wave signals, power-operated means energizable to drive saidtuning instrumentality to tune said receiver over a predetermined rangeof wave-signal frequencies, and a control system responsive to apredetermined amplitude of a received signal translated through at leasta portion of said receiver for deenergizing said power-operated means toterminate variation thereby of said tuning instrumentality, said systemincluding a pair of vacuum-tube electrode structures each having ananode, a cathode and a control electrode with cross connections betweenthe anode of one electrode structure and the control electrode of theother electrode structure to provide a flipflop circuit with an inputcircuit to which is applied a control potential of amplitude varyingwith the intensity of said translated signal and a control circuiteffective to control the energization of said power-operated means.

6. In a signal-seeking receiver, in combination, a tuninginstrumentality which is variable to adjust the tuning of said receiverto desired wave signals, power-operated means energizable to drive saidtuning instrumentalit to tune said receiver over a predetermined rangeof Wave-signal frequencies, and a control system responsive to apredetermined amplitude of a received signal translated through at leasta portion of said receiver for deenergizing said power-operated means toterminate variation thereby of said tuning instrumentality, said systemincluding a flip-flop circuit having an input circuit to which isapplied a control potential of amplitude varying with the intensity ofsaid translated signal and having an output circuit, and a relayincluded in said output circuit for energization thereby and includingrelay elements which are included in an energizin circuit of saidpoweroperated means to control the energization thereof.

'7. In a signal-seeking receiver, in combination,

a tuning instrumentality which is variable to adjust the tuning of saidreceiver to desired wave signals, power-operated means energizable todrive said tuning instrumentality to tune said receiver over apredetermined range of Wavesignal frequencies, and a control systemrespon sive to a predetermined amplitude of a received signal translatedthrough at least a portion of said receiver for deenergizing saidpower-operated means to terminate variation thereby of said tuninginstrumentality, said system including a pair of vacuum-tube electrodestructures each having an anode, a cathode and a control electrode withcross connections between the anode of each electrode structure and thecontrol elec trode of the other electrode structure to vary in oppositesenses the conductivity of said electrode structures, the controlelectrodes of said structures being normally so biased that oneelectrode structure is conductive and the other is non-conductive, meansresponsive to said translated signal for reducing the conductivity ofsaid one electrode structure, whereby a flip-flop action is producedsubstantially cutting off said one electrode structure and renderingsaid other electrode structure conductive, and means responsive to thestate of conductivity of one of said electrode structures for efiectingdeenergization of said poweroperated means,

8. In a signal-seeking receiver, in combination, a tuninginstrumentality which is variable to adjust the tuning of said receiverto desired wave signals, power-operated means energizable to drive saidtuning instrumentality to tune said receiver over a predetermined rangeof wavesignal frequencies, and a control system responsive to apredetermined amplitude of a received signal translated through at leasta portion of said receiver for deenergizing said power-operated means toterminate variation thereby of said tuning instrumentality, said systemincluding a pair of vacuum-tube electrode structures each having ananode, a cathode and a control electrode with cross connections betweenthe anode of each electrode structure and the control electrode of theother electrode structiu'e to vary in opposite senses the conductivityof said electrode structures, the control electrodes of said structuresbeing normally so biased that one electrode structure is conductive andthe other is nonconductive, means responsive to said translated signalfor reducing the conductivity of said one electrode structure, whereby aflip-flop action is produced substantially cutting oil said oneelectrode structure and rendering said other electrode structureconductive, and means responsive to the conductivity of said otherelectrode structure for effecting deenergization of said power-operatedmeans.

9. In a superheterodyne type of signal-seeking receiver having anintermediate-frequency amplifier, in combination, a tuninginstrumentality which is variable to adjust the tuning of said receiverto desired Wave signals, power-operated means energizable to drive saidtuning instrumentality to tune said receiver over a predetermined rangeof wave-signal frequencies, a piezoelectric crystal coupled to saidamplifier and resonant substantially at the mean frequency thereof, anda control system responsive to a predetermined amplitude of a Wavesignal translated through said crystal for deenergizing saidpoweroperated means to terminate variation thereby of said tuninginstrumentality, said system including a flip-flop circuit having aninput circuit to which is applied a control potential of amplitudevarying with the intensity of said translated signal and having acontrol circuit efiective to control the energization of saidpower-operated means.

DANA W. COLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,044,645 Stapleton et al. June16, 1936 2,252,457 Cockrell Aug. 12, 1941 2,304,871 Andrews Dec. 15,1942

